1. Field of the Invention
This invention relates to a microfluidic accumulating and proportioning component.
2. Description of the Prior Art
Microfluidic accumulating and proportioning components in the sense of this application serve for accumulating and/or and proportioning liquids. Such microfluidic components feature microstructures such as capillary channels or ports having characteristic dimensions which, for instance, include the hydraulic diameter of the channels in the range from 5 μm to 1,500 m (preferably from 10 μm to 500 μm) in one dimension. In particular, microfluidic proportioning components may have proportioning volumes in the nanoliter range and microliter range. They may be specifically manufactured from semiconductors and/or plastics and/or glass and/or ceramics and/or metals where appropriate manufacturing techniques of the micro-system technology or microstructuring may be employed, e.g. lithography and etching processes (for semiconductors) or Liga processes (for metals, plastics, and ceramics).
WO 99/10099 describes various microproportioning systems which are intended for proportioning volumes in the range of a few nanoliter up to some microliters and use an open-jet proportioner and/or a micro-diaphragm pump. One of these microproportioning systems has a proportioning and reagent unit. The unit has a reservoir with a filter for pressure compensation with the environment and a micro-diaphragm pump and/or open-jet proportioner connected thereto via a line. It further has an outwardly projecting delivery tube with a proportioning outlet. In addition, there is a proportioning control for the micro-diaphragm pump. The proportioning and reagent unit is adapted to be inserted into a receptacle in the base area of a casing so as to make the delivery tube axially protrude beyond the base area. The proportioning control is connected to an optical sensor fixedly disposed in the casing base which is associated with the delivery tube of the insertable proportioning and reagent unit.
This proportioning system is prepared for operation by inserting a proportioning and reagent unit prefilled with a reagent (e.g. an enzyme) into the receptacle of the casing. In the first proportioning step, the micro-diaphragm pump draws off liquid from the reservoir until the sensor detects the meniscus and, thus, reaches a defined zero position. From this point onwards, the volume to be proportioned is controlled via the known stroke volume of the micro-diaphragm pump. Once the proportioning and reagent unit is empty it is exchanged against a new, prefilled unit.
This document further discloses a microproportioning system with a reservoir having a capillary compensation system, an open-jet proportioner the inlet of which is connected to the capillary compensation system, a proportioning outlet connected to the outlet of the open-jet proportioner and a proportioning control which is in an operative communication with the open-jet proportioner. The capillary compensation system serves for the accumulating and capillary conveyance of the liquid into the open-jet proportioner from the reservoir. Apart from this, it may be used to balance variations of the ambient conditions such as air pressure and temperature and to compensate the liquid volume consumed by the open-jet proportioner. The capillary compensation system prevents the formation of bubbles which could appear in the accumulated liquid volume during an acceleration, e.g. during a fall of the reservoir, and could interfere with the proportioning process. The capillary compensation system may be aerated in at least one point remote from a connection with the open-jet proportioner in order that liquid which flows out be made up for by air which flows in. At the same time, the capillary forces will then prevent leakage from the reservoir. The previously described microproportioning system may also have such a capillary compensation system.
However, a leakage of liquid or formation of bubbles with concomitant liquid losses and faulty proportionings may still occur in the previously described microproportioning system.
Therefore, it is the object of the invention to provide a microfluidic accumulating and/or proportioning component in which the controlled storage and delivery of liquid is further improved.